In map sudoku example the letters B and C in the bottom left and right can be interchanged because we have a B at R2C2 satisfying the condition.

2. POSITION SUDOKU

What is different?
* This will have a (normal) 9x9 sudoku grid.
* The position of every cell is marked with a number from 1-9.
* If the cell value is the same as the position value, then we say that the cell "contains its number".
* For the eight outside boxes, the number of such cells in the box is given. This is also given for the two diagonals.

How to solve
* We need to apply classic rules and also keep counting or eliminating cells which "can have their number".
* If the number of given cells is very high or very low, that box or diagonal could be a place to start.
* Also, you could follow a notation to mark the cells which CANNOT "contain their number" (you could cross or circle the position mark).
* For example, if a '1' is a given number in R2C1 then R1C1, R4C1 and R7C1 cannot "contain their number", and so on. We can mark them as eliminated for counting.
* Also once a box or diagonal has reached its count, we can eliminate the position numbers from the other cells in the box or diagonal respectively.
* Do not confuse between pencilmarks and position marks.

B at R2C2 is not coloured, so it is not a point on the map. So it cannot satisfy the condition.

In maze sudoku, the multiple ckues will be given in the same order. ie if their exists a gap between walls the given multiple clues will be in the same order of walls .Is this true.

Yes. You are right.

The Position Sudoku is still not clear to me. What I understood is only that if a cell contains a number equals to the number at the top right corner of that cell is the cell which contains its number. After that what to do with neighbour cells? And what do the numbers indicate outside the Sudoku box? What does the 'Position' mean here? Is that the position of Row/Column of the cell? Could you please explain the example from the given IB?

Look at the solution. Easier to explain from there. We have three numbers given outside - 2 for box2, 0 for box4 and 2 for one diagonal.
* If you look at box 2, the cells with 3 and 4 "contain their numbers". So there are two cells which "contain their numbers".
* If you look at box 4, none of the cells "contain their numbers". So there are zero cells which "contain their numbers".
* If you look at the marked diagonal, both the 3s "contain their numbers". So there are two cells which "contain their numbers".

Did you get a clarity on the rules, Swagatam?

Edited by rakesh_rai 2015-09-16 10:36 AM

Can we participate in this competition in online mode?

Unfortunately the answer is 'No'. You need to print the pdf and solve it, or solve in paint which may be cumbersome.

I thank Rakesh for detailed responses. They are really comprehensive, so I have not had to engage in a discussion.

For Map Sudoku, my print doesn't show shaded cells. Is it too late to make the Puzzle booklet version have gray cells like the ones used on Mahabharat, etc.?

Yes, I'll do gray cells, if necessary.

IB looks very tough. Thanks to Rakesh for the detailed explanation on position sudoku. Looks clear now. It will be great if the link with more examples could be shared on these types.

3. THREEVISION SUDOKU

What is different?
* This will have a (normal) 9x9 sudoku grid.
* Some dotted boxes will be given. The sum of numbers in these boxes should be a multiple of 3 (3,6,9,12, and so on).

How to solve
* This variant should be much simpler to understand and is not much different from normal variants, in terms of solving.
* Eliminate possibilities from the cells inside the boxes, by utilizing the 3-divisibility rule.
* If it is a box with just one cell, it can be 3 or 6 or 9.
* If it is a box with two cells, the sum can be 3 or 6 or 9 or 12 or 15. Is one number is given, the other number will have limited possibilities.
* The boxes can have any length from 1 to 9.
* Also, note that sum of all numbers in a row/column is 45. So if, for example, N cells are completely covered by a single box. We can conclude that the remaining cells should also add to a multiple of 3. (If X is a multiple of 3, then 45-X is also a multiple of 3). Similar logic can be applied based on how the boxes are placed in the grid.
* For example, in row 1 of the IB grid, R1C4, R1C5, R1C6 add up to a multiple of 3. This means the remaining cells in R1 also add to a multiple of 3. This logic can be especially useful when you have longer dotted boxes.
* Remember the multiplication table of 3 well! and do not forget classic rules.

Yes, it is clear to me now. Thanks Rakesh for clarifying this.

9. FENCES SUDOKU

What is different?
* It is effectively a 6x6 sudoku.
* Each number in the grid shows how many of the four segments around it belong to the digit-fence.

How to solve
* Just replace all the 36 cells with pencilmarks, based on the possible digit fences that meet the given constraints.
* In the IB example, if you look at R1C2, only the digit fences 3 and 5 meet the given constraints where 3 appears two times in the grid. So we put 3 and 5 as pencilmarks in this cell.
* After all pencilmarks are done, solve it as a normal 6x6 sudoku.
* This should be the easiest sudoku in the contest, going by points as well.

8. FLOWER

What is different?
* There are no 3x3 boxes but there will be irregular shapes of differnet sizes.
* Use digits from 1 to 9.
* Digits must be different in every row, column and outlined area.
* Digits must form sets of consecutive numbers in every row, column and outlined area.

How to solve
* Carefully look at the rows, columns and boxes for a start. If there are rows/columns/boxes of smaller length, they may give an opening.
* Not all rows, columns and boxes will be of size 9.
* If it is a row/column/shape of size 2, these numbers have to be consecutive.
* If it is a row/column/shape of size 3, these numbers have to form a set of 3 consecutive numbers.
* If the size is 8, all numbers will be there except 1 or 9.
* If the size is 7, the numbers 3,4,5,6,7 must be present.
* The approach should be to pencilmark the cells and eliminate possibilities based on the "set of consecutive numbers" constraint.
* Keep switching your focus from rows to columns to shapes, so that you make progress.
* Also, remember that the rows and columns may not always be contiguous (as in the IB), so do not forget cells which are in the same line but have some gaps in between.

Edited by rakesh_rai 2015-09-17 5:35 PM

6. TRIMINOES SUDOKU

What is different?
* No rules are given for this.
* But triminoes may be something to do with 3 cells.

How to solve
* There will be an example given in the Puzzle Booklet.
* During the contest, you need to deduce the rules from the example and solve the given sudoku using those same rules.

Covering the rest briefly...

4. DRAW CROSS NUMBER

* Cross number is like a crossword - only we have numbers instead of words.
* All the "branches" of the crossnumber have to be orthogonally connected.
* Mark the cells with cross numbers with circles and those which are not with crosses, for example. (Or you can use two colours also).
* Look for clues or set of clues which cover a large part of the row/column, for starting.
* For example, in the IB, the 3 in the first column effectively means that R2C1 and R3C1 must be part of the cross number.
* Use "1" clues effectively. In the IB, once we find R3C1 as a part of the cross number, we can rule out the other cells in R3 from the cross number.
* Larger numbers in clues can lead to us deducing that certain cells MUST be part of the cross number.
* Most of the times, in such grids, solving part comes after identification of the cross number cells. But if the sudoku can be solved to some extent, it should be done.

5. MAP SUDOKU

* Only the gray cells will be part of map.
* Calculate distances between given cells - focusing on the maximum and minimum possible distances.
* Try to match the given information on distances with the actual ones on map.
* For example, in the IB, it is very obvious that R1C2 and R4C3 have to be C and A respectively.
* Once you get a start, try to use ALL given information on distances, eliminate possibilities and complete the map cells.
* Also keep solving simultaneously. You may need to switch between solving the sudoku and identifying the map elements at times.

7. MAZE SUDOKU

* There have to be 12 cells in each maze. A maze cannot have less than or more than 12 cells.
* Based on the given information on walls, we can come up with wall segments which are DEFINITELY present. For example, the 4 clue in the IB.
* Use the "continuously visit" logic to eliminate possibilities. There has to be a connected path from 1 to 12 within every maze.
* The solving involves confirming and eliminating wall possibilities.
* There has to be at least a one cell gap between successive wall segments.
* Solve the IB example to get a good idea of the technique involved.

That was fun.

It took me unnecessarily long to spot the Extra Region concept of Position Sudoku. Kept going back to it about 5 times over the contest and kept thinking there's something I'm missing. Typically enough, it struck me with about 3 minutes to go and I couldn't finish on time. Ah well.

to inform about all ruls

Edited by Priya Jaiswal 2015-09-20 1:38 PM

The question is not clear.

Right now, I'm mostly upset as I ran out of time while inputting the solution to Flower and missed the points for it by at most 5 seconds... Grrrrrrrrrrr... but it was a really nice test. Thanks a lot Riad for beautiful puzzles.

I've been watching you since the 80 th minute you had already 358 points. It seemed to me that Denis is able to overcome the 500-point line. Every 5-10 minutes I updated the page with the results. Now it is clear that become a hindrance to you. Very interesting and unusual to play the role of impartial observer and potential fans however.